The present invention generally relates to communication systems for full duplex frequency division multiplexed transmission. The present invention relates more particularly to a transceiver, a communication system using a transceiver, and methods related thereto and used therewith.
Traditionally the coupling impedances are matched to the impedance of a transmission medium in order to receive at a receiving means the maximum of the transmitted power. For transmitting, however, these impedances are undesired because they imply that more signal power has to be delivered by the transmission means.
One known solution consists of partially reducing the values of the coupling impedances. This reduces the transmitting signal power requirement but also causes an undesirable additional attenuation of the receiving signals. Another solution is generally described in EP 901221 A1 and in EP 1220444 A1. This solution consists of synthesizing the coupling impedances by using operational amplifiers with positive feedback. This approach also has significant drawbacks. If, for instance, the impedance of the transmission medium increases the required signal output of the operational amplifiers also increases which can cause undesirable signal clipping or may require increasing the supply voltage of the operational amplifiers. Increased supply voltage, however, causes additional undesirable power dissipation. Another disadvantage of this method is that it uses positive feedback, which makes it inherently more prone to oscillations.
The present invention solves the aforementioned exemplary problems, and/or other problems in the art, and provides a transceiver with reduced signal power requirements and high signal power of the receiving signal.